Editor's Note: This story, originally published Sept. 8, was rewritten Sept. 9 with new information. This probably won't be the only time we update it.

The iPhone 7 and iPhone 7 Plus are being sold by all five major US carriers. But Apple's pre-sale website now confirms there are two different models of iPhone 7 and iPhone 7 Plus sold in the United States. The one sold by AT&T and T-Mobile will never support Verizon's or Sprint's CDMA networks, so if you want a phone that works on all four carriers, you need to get the Verizon or Sprint models.

Apple's official spec sheet for the iPhone 7 lists two sets of units sold in the US. Models A1660 (iPhone 7) and A1661 (iPhone 7 Plus) work on all four major US networks and virtual networks like Ting, Ultra Mobile, and Consumer Cellular. Models A1778 (iPhone 7) and A1784 (iPhone 7 Plus), according to Apple's Web page, do not have CDMA modems and thus don't work on Verizon, Sprint, or any smaller carrier that uses those networks.

All of the models work equally well on most other countries' networks except on China Mobile, which requires A1660/A1661. Japan has its own unique set of models, probably because of the country's Felica mobile payment system.

Additionally, we've now discovered that you can't pre-order one of those phones online without a Verizon or Sprint subscription. But former Apple exec and analyst Michael Gartenberg points out on Twitter that once Sept. 16 rolls around, you'll be able to show up at an Apple store and buy a Verizon phone at full price. That's your best bet now, if you want an all-carrier-compatible iPhone.

Whether you go with Verizon or Sprint depends on which carrier you intend to use it on first. If you're going to use it on Sprint, buy the Sprint phone, but understand it will be locked to Sprint for 50 days. Everyone else who wants an all-carrier-compatible phone should get the Verizon unit, which is factory unlocked. (In the initial weeks after the release of a new iPhone, there's always some confusion with Sprint not activating Verizon devices, which doesn't have to do with whether or not the phone is unlocked.)

People outside the U.S., Japan and China should be less concerned. All of the iPhone 7 and iPhone 7 Plus models look like they work on the same international frequency bands and networks outside those three countries. But there's still a possible concern which I'll get to below.

What's Really Going On Here?There are a few possibilities regarding what Apple is really doing here; we probably won't know the full answer until iFixit and Chipworks do their teardowns of the new phone next weekend.

But the secret may lie in this Bloomberg story saying that Apple moved to Intel modems for some number of iPhones, which would be the AT&T and T-Mobile models. We reported this rumor as far back as 2015, and it was widely echoed in the financial and trade press in mid-2016.

That would mean that while the Sprint, Verizon, Japanese, and Chinese units are probably running Qualcomm's X12 modem, which is the same one used in the Samsung Galaxy S7 and other top smartphones right now, the AT&T and T-Mobile models probably use Intel's XMM7360. Intel's modems don't support CDMA.

Please understand that this is all (informed) speculation. I'm getting radio silence from Apple right now, and Qualcomm, Intel, and all of the carriers have just pointed me back to Apple for comment.

If Apple has gone with Intel, that's Apple getting back to its roots. The first iPhones used modems from Infineon, which was purchased by Intel and became Intel's modem division. But I'm a bit concerned because while the X12 is the current gold standard for modems, we've never seen the XMM7360 in any US phone, although it's been on the market since late 2015. So we don't know anything about the real-world performance of the XMM7360 versus the X12. That's relevant because a phone's modem, which controls its connection to the Internet, is a very, very important part.

Intel's XMM7360 does not support the newest network features like 256 QAM and 4x4 MIMO, which are part of T-Mobile's latest network upgrades. But those features are optional on the X12, so Apple's X12 may not support them either. We don't know. The Intel and Qualcomm modems may or may not have the same overall LTE performance. We don't know that yet either.

There's another theory, too: that all of the iPhones use Qualcomm modems but that for some reason, Apple disabled the CDMA radios in half of them. That makes less sense to me than the Intel theory, but you can add it to the "we don't know" list.

Related

What's Apple thinking? Remember that Apple CEO Tim Cook is the master of the supply chain. Ordering components from two different competitors, known as "dual sourcing," is a common way companies gain negotiating power and lower prices. Last year, Apple dual-sourced its A9 chips from Samsung and TSMC, resulting in "similar but not quite equal" chips, according to Anandtech. After considerable stress and worry, various analysts determined that the performance difference between the chips could be less than the performance variance within an individual batch of chips, making it pointless to seek out one or the other.

Putting Intel in the AT&T, T-Mobile and European iPhones gives Apple more leverage over Qualcomm and makes it less dependent on Qualcomm's production capabilities. I will continue to update this story as I learn more.

About the Author

PCMag.com's lead mobile analyst, Sascha Segan, has reviewed hundreds of smartphones, tablets and other gadgets in more than 13 years with PCMag. He's the head of our Fastest Mobile Networks project, hosts our One Cool Thing daily Web show, and writes opinions on tech and society.
Segan is also a multiple award-winning travel writer. Other than ... See Full Bio

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